Flow control valves are frequently used to regulate flow through piping systems and the like. In one type of flow control valve, an electro-magnetic actuator in the form of a solenoid is utilized to regulate flow through a cooperating valve assembly. Such actuators ordinarily comprise a hollow guide tube with a passageway formed therein, an electrically energizable solenoid coil wrapped around the guide tube, and a magnetic armature or a plunger slidably disposed within the passageway of the guide tube and interacting with the valve assembly. When an electric current is passed through the solenoid coil, a magnetic field (or flux) is produced within the guide tube which moves the armature along the passageway and causes flow through the valve assembly which is proportional to the current applied to the coil.
A proportional priority flow regulator is a specific type of flow control valve used to regulate fluid flow on a priority basis. Proportional priority flow regulators are typically used in lifting devices, such as material handling, agriculture and construction equipment, to allow an operator to raise a load at a controlled speed by directing a high-pressure fluid to a single acting cylinder over a regulated line. Lowering the load is usually accomplished by the force of gravity, requiring the use of additional flow control devices such as flow regulators, directional valves, check valves, and the like to control the flow fluid from the lifting device to an overflow tank and thereby control the rate of descent of the load.
It would be more economical to use a single regulator for directing fluid to the lift as well as for directing the excess fluid to an overflow tank. However, conventional proportional priority flow regulators can only provide controllable flow in one direction--from the high-pressure input to the regulated line.